Protecting cargo in an uncontrolled environment (e.g. out of doors on the city streets, at a rest stop, etc.) is problematic. Providing security coverage for a long, rectangular area can be particularly difficult in instances wherein monitoring employs the use of circular patterns as is the case with a transmitter of electromagnetic radiation from a point source. Similarities exist in this instance and with the case of providing lighting on a winding street in a city neighborhood. Light may be desired for the street but not necessarily for areas located along the street such as houses and yards. Use of a circular light pattern to illuminate a street would likely result in illumination of unwanted areas as well. Moreover, the circular light pattern would more likely result in unlit spots on the street together with lighted areas adjacent the street.
Security coverage furnished by radiating an invisible electromagnetic point source encounters a similar problem, whether that source be a microwave emission from a field disturbance sensor (FDS) or otherwise. Just as it would be desirous to provide lighting for a street with a lighting pattern that is only as wide and as long as the street itself, a need exists to be able to provide security coverage through the use of electromagnetic monitoring that protects a coverage area outlining an odd or oblong shape such as that of a commercial truck and/or trailer. Conventional field disturbance sensors for electromagnetic field disturbance intruder detection generally employ a patch antenna that creates a spherical shaped coverage area. In order to sufficiently protect a tractor trailer with a FDS that emits a circular, mushroom shaped field, it would be necessary to install two, three, four or more additional field disturbance sensors in order to cover field gaps created by metal objects such as wheels, an engine, a transmission, a chassis, etc. A need exists to provide security protection for a large object such as a truck and trailer. Further, a need exists to provide security protection for a large object such as a trailer wherein advance warning, such as a proximity alert, is generated in response to someone entering a protected area around that object.
Applicable reference numerals have been carried forward.